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A study published Feb. 14 in the American Journal of Cardiology suggests obese patients with atrial fibrillation (AF) fare better in terms of mortality and stroke events than their non-obese counterparts—a finding that’s in line with the much-contested “obesity paradox.”

The obesity paradox, or the idea that obese patients see some kind of cardioprotective benefit as a result of their weight, hasn’t been studied in the context of AF, Manyoo A. Agarwal, MD, of the University of Tennessee Health Science Center, and colleagues wrote in AJC.

“While obesity is an independent risk factor for the incidence and progression of cardiovascular diseases, data suggests a better prognosis in obese patients with CVD than non-obese cohorts,” the authors said, referencing earlier research. “Obesity adversely impacts cardiovascular hemodynamics and cardiac structure and function, and is an independent risk factor for AF.”

Agarwal et al. drew data from the National Inpatient Sample (NIS) between 2010 and 2014 to identify all adult hospitalizations in the country with a primary diagnosis of AF. The researchers considered patients obese if they met the comorbidity variable for obesity defined by the NIS.

The authors compared in-hospital outcomes, including mortality and acute stroke events, between non-obese patients and obese patients with AF. Of a cumulative 431,734 hospitalizations for AF during the study period, 66,138 patients—or 15.3 percent—were obese.

They said obese patients were more likely to be younger and black, but despite being younger those who were obese also had a higher prevalence of CV comorbidities like hypertension, diabetes, dyslipidemia, smoking, heart failure and chronic renal failure. After multivariate risk adjustment, obese patients had a lower in-hospital mortality than non-obese patients (0.5 percent vs. 1 percent, respectively) and fewer acute stroke events (0.4 percent vs. 0.7 percent).

“Interestingly, we found a paradoxical inverse association between short-term outcomes and obesity in AF hospitalizations,” Agarwal and co-authors wrote. “Obese patients are younger than non-obese counterparts at the time of presentation, plausibly due to factors such as poorer functional status and lower atrial natriuretic peptides, which in turn can lead to medical care at a younger age and ability to receive and better tolerate therapies like beta-blockers.

Other than that, we know little about the obesity paradox, Agarwal et al. said, and the authors urged readers to take their findings with a grain of salt.

“It is vital to emphasize that our paradoxical observation of favorable survival outcomes in obese AF patients does not assume causation and must not be seen as encouragement for weight gain,” they wrote. “The obesity paradox demands further research to better understand and utilize this noteworthy observation for improving patient care and prognosis.”